Bluetooth: btusb: Remove detection of ISO packets over bulk

This removes the code introduced by
14202eff as hci_recv_frame is now able
to detect ACL packets that are in fact ISO packets.

Fixes: 14202eff ("Bluetooth: btusb: Detect if an ACL packet is in fact an ISO packet")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>